DeKok and Variations on Murder

As has been her habit since the death of her husband, Mrs. Van Haesbergen does nightly rounds in the large office building where she resides. Her husband had been the building superintendent, and an apartment on the top floor came with the job.
One night she encounters the managing director in the boardroom, sitting in his chair at the head of the table. She hastily walks up to him, and to her horror, she finds him dead. She rushes up to her apartment to call someone, but who? Deciding it better to return to the boardroom to determine what exactly happened, she finds the dead man gone...
Soon after she learns that the director is on holiday in the Bahamas. With unbearable visions of him dead in the boardroom, she turns to Inspector DeKok for help.